linux-kernel - Re: [PATCH v3 0/9] Tegra xHCI support

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Message-ID: <5418C1C7.90404@wwwdotorg.org>
Date:	Tue, 16 Sep 2014 17:03:35 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Andrew Bresticker <abrestic@...omium.org>
CC:	Tomeu Vizoso <tomeu@...euvizoso.net>,
	Thierry Reding <thierry.reding@...il.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Grant Likely <grant.likely@...aro.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Arnd Bergmann <arnd@...db.de>,
	Kishon Vijay Abraham I <kishon@...com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v3 0/9] Tegra xHCI support

On 09/16/2014 04:51 PM, Andrew Bresticker wrote:
> On Tue, Sep 16, 2014 at 3:40 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 09/16/2014 10:57 AM, Andrew Bresticker wrote:
>>> On Tue, Sep 16, 2014 at 8:26 AM, Stephen Warren <swarren@...dotorg.org> wrote:
>>>> The XHCI driver can't load its firmware unless it's a module; if I make it
>>>> built-in, it fails immediately with error -2 during "Direct firmware
>>>> loading". The driver needs to work with either immediate or deferred
>>>> firmware loading.
>>>
>>>
>>> If you want the driver to be built-in, you'll either need to build the
>>> firmware in as well (i.e. EXTRA_FIRMWARE) or enable
>>> FW_LOADER_USER_HELPER_FALLBACK to load with userspace/uevent (though
>>> apparently this is deprecated).
>>
>>
>> Hmm. I didn't have to do that for the Atmel touchpad driver to work, but
>> perhaps it's just ignoring a firmware loading error, and continuing with
>> whatever is in the device's flash already.
>>
>> It seems odd that such a fundamental feature would require a deprecated
>> Kconfig option. Is there some replacement that does the same thing that
>> isn't deprecated? The Kconfig help for the option doesn't say anything
>> useful...
>>
>> Oh, this option doesn't actually seem to work. I see the following in dmesg:
>>
>>> [root@...rren-dt ~]# dmesg|grep -i -e xhci -e firmware
>>> [    1.461773] xhci-tegra 70090000.usb: Failed to get supply 'avddio-pex':
>>> -517
>>> [    1.468930] platform 70090000.usb: Driver xhci-tegra requests probe
>>> deferral
>>> [    2.567966] xhci-tegra 70090000.usb: Direct firmware load for
>>> nvidia/tegra124/xusb.bin failed with error -2
>>> [    2.577786] xhci-tegra 70090000.usb: Falling back to user helper
>>
>>
>> ... but:
>>
>> [root@...rren-dt ~]# lsusb
>> unable to initialize libusb: -99
>>
>> Perhaps systemd-udevd doesn't implement firmware loading; is it user-space
>> udev that's deprecated implementing user-space firmware loading, rather than
>> the kernel deprecating support for calling out to user space?
>
> I believe it is userspace udev that has deprecated user firmware
> loading.  The kernel still does call out to userspace.  Alternatively,
> you could use the firmware_class loading interface described in
> Documentation/firmware_class/README, but that kind of sucks too.
>
>> This sucks, because now I can't just TFTP boot kernels but somehow have to
>> get updated kernel modules onto my device every time before testing a new
>> kernel build.
>
> Yeah... it does.  I get around this by building the firmware into the
> kernel image (i.e. CONFIG_EXTRA_FIRMWARE), which is also your only
> option if the root device happens to be on USB.  Unfortunately, I'm
> not aware of any other alternatives.

Ah right, CONFIG_EXTRA_FIRMWARE does work, although it's not something I 
can put into tegra_defconfig for people. I suppose we'll have to make it 
=m in tegra_defconfig, and anyone who wants to build it in will have to 
carry a local patch to add the firmware to their kernel source tree. At 
least with "git add" of the firmware, it won't disappear from disk upon 
"git clean ...".
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